The inventive concepts disclosed herein are generally directed to waste stream management systems. More particularly, but not by way of limitation, the inventive concepts disclosed herein are directed to a waste stream management system for controlled land application of contaminants from waste stream fluids.
Multiple human activities produce waste streams which include various contaminants at varying concentrations, and which are managed in various manners. For example, municipalities produce waste streams (e.g., sewage), that include fluids which are typically processed and/or treated before being returned to the environment. Further, industrial and agricultural operations generate varying contaminant concentration waste streams that likewise are processed or treated to minimize the environmental effects of the contaminants contained therein. For example, waste streams from paper mills, industrial facilities, poultry processing plants, slaughter houses, and other industrial, agricultural, or municipal sources include contaminants at varying concentrations, and the particular contaminants present in a waste stream and their respective concentrations generally guide the appropriate method of management of the waste stream.
The oil and gas industry produces multiple waste streams at various stages of oil and gas well development and exploitation, which include water-based fluids and/or solids such as drilling mud and flowback water, oil-based fluids and solids, and other similar waste streams, which are disposed of in compliance with a variety of environmental regulations. For example, prior art oilfield waste stream management practice has been to deposit used drilling mud into a mud pit at the well site, where the drilling mud is simply encased in a layer of dirt after the well is completed. The encased drilling mud remains at that location indefinitely, increasing the potential for contamination of adjacent soils, and surface and subsurface waters.
In recent years, due to increasing environmental concerns and strict legislative regulation and oversight, conventional industrial, municipal, and agricultural waste stream management practices have faced increased scrutiny, and multiple improvements and changes to such practices have been proposed and/or mandated to protect the environment.
One such proposed waste stream management practice has been to apply waste streams on a tract of land to spread the contaminant(s) present in the waste stream over a land area such that the concentration of contaminants per area of land is well below safe levels for each contaminant as set by applicable laws or regulations. In some instances, the land application of waste streams not only does not harm the land area or soil onto which the waste stream has been applied, but actually improves the usability of the tract of land as agricultural land.
Several systems have been recently proposed to apply waste streams to land. For example, the system described in U.S. Publication No. 2011/0266357, the entire disclosure of which is hereby expressly incorporated herein by reference, uses a constant flowrate on/off 4-inch valve, which is opened when an applicator vehicle is moving above a predetermined minimum speed, so that a rate of application when the valve is opened and when the applicator vehicle is moving above the predetermined minimum speed does not exceed a predetermined maximum application rate.
However, applying waste streams at a constant flowrate is generally suboptimal, as such application may result in applying a lower level of contaminants than allowed by applicable regulations by not fully utilizing the available area of land, thus leaving a substantial unused contaminant loading capacity in the land area. Further, in some instances where the predetermined minimum speed cannot be achieved or maintained by the applicator vehicle (e.g., when the applicator vehicle moves up or down a hill, and/or over slippery or rough terrain) the application is discontinued for any periods of time when the applicator vehicle is moving below the predetermined minimum speed. This results in significant loss of time for the operator of the applicator unit. Simply driving the applicator vehicle over the land area without applying waste stream fluids unnecessarily increases the land area needed to manage a given volume of waste stream fluids and the overall waste stream application times, and results in increased fuel and other costs. Finally, requiring the applicator vehicle to move at or above a predetermined minimum speed over rough terrain increases applicator vehicle maintenance costs and downtime.
Further, applying waste streams at constant flowrates limits the usability of the applicator vehicle where the concentrations of contaminants vary over time or per each load of waste stream fluids, such as when a live waste stream has to be managed which is often the case in oil and gas operations. For example, when the level of contaminants in a particular load of waste stream fluids from a live waste stream is higher than expected, applying at a constant rate may not be feasible, as the applicator vehicle may be unable to achieve a high enough speed to apply the waste stream at an acceptable application rate. Further, when the level of contaminants in a particular load of waste stream fluids from a live waste stream is lower than expected, applying at a constant rate at the predetermined minimum speed would leave a significant contaminant capacity in the land area and significantly underutilize the available land area. Managing a waste stream with variable contaminant concentrations with constant flowrate application systems may result in inaccurate measurement of the actual amount of contaminant applied to the land area, which would make repeated applications on the same land area extremely risky and/or practically impossible.